{"id":2696,"date":"2026-08-07T16:10:30","date_gmt":"2026-08-07T14:10:30","guid":{"rendered":"https:\/\/stage.dekozell.de\/?p=2696"},"modified":"2026-09-25T12:17:42","modified_gmt":"2026-09-25T10:17:42","slug":"sabine-formula","status":"publish","type":"post","link":"https:\/\/dekozell.de\/en\/sabine-formula\/","title":{"rendered":"Sabine Formula"},"content":{"rendered":"

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Fundamentals & Calculation<\/div>\n

Calculating reverberation time: the principle of the acoustically open window<\/h1>\n
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\nAuthor:<\/strong> Thomas Neubauer, Managing Director of DEKOZELL, has 20 years of experience in the development and application of acoustic plaster. He personally reviews and takes responsibility for every article.<\/div>\n
\n21 July 2026<\/span>
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\n8 min read<\/span><\/div>\n<\/div>\n

In our last article Improve room acoustics<\/a> we looked at why rooms reverberate and what can be done about it. But one question remains, and it is crucial to every acoustic design: How much sound absorption does a room actually need to become quiet? And how can you know before the first bag of plaster is even mixed? The answer lies in a surprisingly simple concept: the acoustically open window. With this concept and a single equation, the reverberation time can be calculated.<\/p>\n

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The open window as the perfect sound absorber<\/h2>\n<\/div>\n

When sound hits a surface, part of it is reflected and part of it is absorbed. The proportion that is absorbed is described by the sound absorption coefficient α:<\/p>\n

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  • α = 0:<\/strong> All of the sound is reflected. Example: a closed window or a hard, smooth wall.<\/li>\n
  • α = 1:<\/strong> All of the sound is absorbed; nothing is reflected back. Example: an open window, where the sound simply escapes outside.<\/li>\n<\/ul>\n

    Real materials usually fall somewhere between 0.2 and 0.8, and the value depends on frequency. An open window therefore represents the theoretical ideal: one hundred percent absorption. That is exactly why it works so well as a reference for everything else.<\/p>\n

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